1. Technical Field
This invention relates to heat exchangers for refrigeration circuits, and more particularly, to an evaporator for an automotive air conditioning refrigeration circuit.
2. Description of the Prior Art
Evaporators for use in automotive air conditioning refrigeration circuits are known in the art. With reference to FIG. 1, serpentined type evaporator or heat exchanger 10 is shown. Evaporator 10 includes continuous serpentined tube 11 through which refrigerant fluid flows. Serpentined tube 11 includes a plurality of spaced parallel planar portions 12 and a corresponding plurality of curved connecting portions 121. Air flows through evaporator 10 between planar portions 12 in the direction of the arrow shown in FIG. 1. As shown in FIG. 2, the interior space of serpentined tube 11 is divided by a plurality of parallel partition walls 111 into a corresponding plurality of essentially parallel passages through which refrigerant fluid flows. One terminal end of serpentined tube 11 is brazed to fluid inlet pipe 15 which is linked to the output of a compression or an expansion means (for example, a compressor, not shown) of a refrigeration circuit. A second terminal end of serpentined tube 11 is brazed to fluid outlet pipe 16 which is linked to the inlet of the compressor. Refrigerant fluid is provided to serpentined tube 11 from the compressor via inlet pipe 15, flows through each successive planar portion 12 and connecting portion 121 towards outlet pipe 16, and is then returned to the compressor. Of course, the refrigeration circuit may include other elements disposed between the compressor and evaporator 10.
With reference to FIGS. 1, 3 and 4, evaporator 10 further includes corrugated heat receiving metal sheet or fin units 13 disposed between opposed planar portions 12. Fin units 13 are fixed to planar portions 12 by brazing along the lines of contact. Protective side plates 14 are fixed to the exterior side of each of the outside fin units 13. Corrugated fin units 13 are formed in a continuous wave shape with a plurality of essentially parallel planar surfaces 13a and curved connecting surfaces 13b. Louvers 17 are cut out of and formed through surfaces 13a as shown in FIG. 4. Fin units 13 exchange heat from the air flowing through evaporator 10 with the refrigerant fluid flowing through serpentined tube 11. Thus, the air flowing through evaporator 10 is cooled. Louvers 17 increases the heat receiving capacity of fin unit 13.
With reference to FIG. 5, a cross-section of corrugated fin unit 13 in accordance with the prior art and a cross-section of planar portion 12 are shown. Louvers 17 extend across surfaces 13a and terminate at side ends 17a, near connecting portions 13b. Side ends 17a are displaced a distance "1" from the surfaces of planar portions 12. Distance "1" is measured in the horizontal plane and includes the displacement due to connecting portions 13b which are in contact with the surfaces of portions 12
In the prior art of FIG. 5, the distance "1" was selected from a range of over 1.0 mm to under 2.0 mm. However, in the prior art, a considerable amount of condensed water becomes trapped between side ends 17a of louvers 17 and the surfaces of parallel portions 12 due to the surface tension of water. The trapped water increases the ventilation resistance of the heat exchanging apparatus, thereby decreasing the heat exchanging efficiency. Additionally, considerable amounts of the compressed water may be scattered into the passenger compartment of an automobile.